a) Field of the Invention
This invention relates to winches and in particular to a form of winch known as a gypsy, in which a flexible pulling element takes a single turn around a driven rotatable sheave. The flexible pulling element may be a rope, a chain or a combination of these. The latter is most familiar in the marine context where the minor portion of the element closest to an anchor is usually chain but the major portion, that which is closer to the boat, may very well be rope.
b) Description of Related Art
Problems in this type of winch are ensuring as far as possible good grip between the sheave and the flexible element and these problems are particularly acute when the element is a mixed rope and chain and/or when there are irregularities in the flexible element such as twists, knots or thickenings.
It has previously been proposed to provide a pivoting arm or a pivoting spring arm to urge the flexible element into the groove of the sheave. See for example GB-A-2233623, U.S. Pat. No. 5,402,985 (both having pivoted arms) and WO-A-96/09980 where a part described as a guide arm is rigidly attached to a housing at one of its ends.
A guide arm rigidly fixed at one end will if it is entirely rigid jam if there is any thickening in the flexible element passing it or will have to rely on its own inherent resilience to exert an effective force on that element.
A problem with the spring constructions is that they urge the flexible element inwardly only at one radius of the sheave so that, if it is desired to pay out rather than pull in the flexible element, there is no provision for maintaining what is now the incoming side of the element in contact with the sheave and it may escape, come loose, tangle or twist.